The governor, a Democrat, signed the legislation Feb. 13 as local state Sen. Cheryl Pflug and other supporters looked on from the packed State Reception Room at the Capitol.

The landmark legislation put Washington among the half-dozen states and Washington, D.C., to allow same-sex marriage, but the measure could face a challenge on the November ballot before any weddings occur.

“It is a day historians will mark as a milestone for equal rights — a day when we did what was right, we did what was just, and we did what was fair,” Gregoire said. “We stood up for equality and we did it together — Republicans and Democrats, gay and straight, young and old, and a variety of religious faiths. I’m proud of who and what we are in this state.”

The legislation cleared the state House of Representatives in a 55-43 decision Feb. 8 — the last hurdle before the measure reached the governor. Republican Glenn Anderson joined local Democrats in the House to approve a landmark bill to legalize same-sex marriage.

Other Issaquah lawmakers joined the majority on the decision. The delegation is comprised of Democrats, except for Anderson and state Rep. Jay Rodne.

Rodne opposed the measure to allow same-sex marriage. The legislator, a North Bend Republican, asked for a referendum clause to send the issue to voters in November, but the proposed amendment failed.

“For the first time in Washington history, the state will sever a relationship with one of the child’s biological parents,” Rodne said amid the debate on the bill.

Anderson, a candidate for lieutenant governor, announced plans to support the measure in a meticulously researched 1,182-word statement last month.

The decision in the House came a week after state senators approved a similar same-sex marriage bill in a 28-21 majority. Issaquah legislators in the upper chamber — Democrat Rodney Tom, and Republicans Pflug and Steve Litzow — supported the Senate bill.

So far, Connecticut, Iowa, Massachusetts, New Hampshire, New York and Vermont — plus Washington, D.C. — allow same-sex marriage. Washington state has had a domestic partnership law — or “everything but marriage” law — in place since 2009.

The push to legalize same-sex marriage still faces hurdles. Opponents pledged to challenge the same-sex marriage law on the November ballot.

Under state law, a referendum could not be filed before Gregoire signed the legislation. Opponents have 90 days from the end of the legislative session — March 8 — to collect 120,577 signatures to put a referendum on the ballot.

If opponents fail to gather enough signatures to hold a referendum, same-sex marriages could start in June. If the measure goes to voters, election results determine whether same-sex marriage proceeds.

King County Executive Dow Constantine praised the decision as an “historic” milestone and pledged to uphold the measure.

“No doubt this law will be challenged. I will work in whatever capacity I can to ensure its approval by Washington voters, just as I fought against the so-called Defense of Marriage Act more than a decade ago,” he said in a statement. “I look forward to the day when I can sign King County’s first marriage license for a same-sex couple.”